The rHPIV1-C(R84G/del170)HN(T553A)L(Y942A) virus vaccine candidate has been given to 35 unscreened healthy adult volunteers. Only 4 of 35 were infected and vaccine virus was shed in minimal amounts with no associated respiratory illness. This indicated that this vaccine was safe to proceed to the next study group, namely seropositive children 15 to 59 months of age. 13 subjects have enrolled (out of the final number of 15, with a vaccine to placebo ratio of 2:1). Of the 6 recipients of vaccine that have been unblinded to date, none shed virus and there were no adverse events. This study is not complete, but these results suggest that this vaccine will be safe to proceed to the next study group, which will be seronegative children 6 to 59 months of age (N = 30, with a vaccine to placebo ratio of 2:1). HPIV2 vaccine: We previously used reverse genetics to generate a live attenuated intranasal HPIV2 vaccine called rHPIV2-V94(15C)/948L/1724 that, like the HPIV1 candidate, included stabilized mutations. This virus was immunogenic and protective in African green monkeys. This vaccine candidate has been given to 15 seropositive adult volunteers. Only 4 were infected and vaccine virus was shed in minimal amounts, which is the desired safety profile for an attenuated virus. The virus is safe to proceed to the next study group, which will seropositive children 15 to 59 months of age (N = 15, with a vaccine to placebo ratio of 2:1). Serologic screening and enrollment is in progress. HPIV3 vaccine: There are two HPIV3 vaccine candidates in ongoing clinical trials. (i) The first is rB/HPIV3, which is recombinant chimera consisting of bovine PIV3 (BPIV3) in which the F and HN protective antigen genes have been replaced by those of HPIV3. The BPIV3 backbone provides a host-range attenuation phenotype to which each of the genes contributes. Studies have been completed in unscreened adults (N =15) and seropositive older children (N = 15, with a vaccine to placebo ratio of 2:1). Minimal shedding was seen in either populations and there was no difference in illness between vaccinees and placebo recipients. Thus, the virus was safe to proceed to seronegative older children of 6 to 36 months of age (N = 30, with a vaccine to placebo ratio of 2:1). 11 subjects in this study group have been enrolled. In the 6 vaccinees and 3 placebo recipients unblinded to date, the vaccine replicated to a moderate titer in most recipients and was well tolerated. (ii) The second HPIV3 candidate is rHPIV3cp45. This is a recombinant version of a biologically derived virus that previously had been found by LID and collaborators to exhibit satisfactory infectivity, safety, immunogenicity, and lack of transmissibility in seronegative infants and children. LID re-derived this virus from cDNA to provide a known pedigree for safety reasons, and the attenuating mutations were identified as described in previous reports. A new vaccine lot was manufactured by LID and is currently being evaluated by LID and Medimmune under a CRADA. LID has found that the cDNA-derived HPIV3cp45 vaccine replicates to over 7log10 TCID50/ml in Vero cells, which is promising for the purposes of manufacture. The vaccine was evaluated at a dose of 5.0 log 10 in a 2-dose, double-blind, placebo controlled trial in 16-12 month old serologically-unscreened infants. 12 of the 16 infants receiving the first dose shed vaccine virus at low-to-moderate titers. Respiratory or febrile illness was observed in 40% of vaccinees and in 38% of placebo recipients. 10 of 15 vaccinated children and none of the 8 placebo recipients had a 4-fold or greater rise in virus-specific serum antibody titer. Thus, the vaccine was well-tolerated and immunogenic in young infants. Each of the 5 vaccinated children who did not respond had some level of pre-existing virus-specific antibody, which likely restricted immunogenicity of the vaccine virus. This indicates that future studies in this population should be performed with individuals who have been pre-screened to be seronegative. Following the second dose, given after a mean interval of 6 weeks, only 1 of 15 vaccinees shed vaccine virus;this individual was asymptomatic. 13% of recipients of the second dose had respiratory or febrile illness, compared to 63% of the second dose placebo group. None of the vaccinees or placebo recipients had a 4-fold rise in virus-specific serum antibody titer following the second dose. This indicates that the vaccine indeed induced protection against HPIV3 infection, and that a longer interval between doses may be needed to obtain a boosting effect. This protocol was amended to include screening to ensure that the infants are HPIV3-seronegative prior to immunzation. The age group has been expanded to include infants and children ages 6 to 36 months. In addition, nasal washes for viral assay were collected only in the case of respiratory or febrile illness. 21 additional subjects were enrolled: 14 received 2 doses of vaccine and 7 received 2 doses of placebo. Rhinorrhea was the most frequently observed illness in either group, occurring in 6/14 vaccinees and 5/7 placebo recipients following the first dose and 5/14 vaccinees and 3/7 placebo recipients following the second dose. 4-fold or greater rises in HPIV3-specific serum antibody were observed in 79% and 14% of vaccinees following the first and second dose, respectively. 86% of vaccinees had a 4-fold or greater rise following either dose. Under a separate protocol, the effect of increasing the interval between the 2 doses to 6 months will be evaluated. 40 children will be enrolled in order to have at least 30 evaluable subjects. Seattle Childrens Hospital has enrolled the first 10 subjects into this study. RSV vaccine: Medimmune has initiated studies under the CRADA leading up to a Phase 2b proof of principle efficacy trial with a recombinant rRSV, called rA2cp248/404/1030delSH, containing a set of five independent attenuating mutations. LID also has manufactured clinical lots of two versions of an RSV mutant in which the M2-2 gene has been deleted, in preparation for Phase 1 studies. Manufacturing is in progress for a mutant containing a deletion in the NS1 gene. HMPV vaccine: LID has submitted an IND application for a clinical lot of a live-attenuated HMPV vaccine virus (rHMPV-Pa) in which the HMPV P gene was replaced by that of avian MPV, thus conferring a host range attenuation phenotype. We also are evaluating a recombinant wild type HMPV in adults in an inpatient study to characterize infectivity, shedding, symptomology, and immune responses. This wild type virus is the parent for all of our HMPV vaccine candidates, and this study will establish the suitability of this virus as the parent as well as providing an indication of its virulence.